For example, an advert that targets everyone within a 10-mile radius of a medium-sized British town (Dorking) is valued at 28p per click by Facebook's advertising tool. However, targeting single gay men in the area with a preference for nightclubbing raises the price to 71p per click — 2.5x the price of targeting the general public.

Such precise targeting also raises other issues. Whittling down ads to target such precise demographics can result in ads targeting as few as 20 people, making it theoretically possible to identify those targeted. "I think the worst scenario might be where someone who hates gays uses Facebook’s targeting to identify gay users and later attack them,”scientific director of the Max Planck Institute for Software Systems."

The worst thing that director can think of happening is a single psychopath using that information to attack people? Maybe my tin foil hat is showing, but isn't it a lot more scary to have detailed demographic lists in the hands of a government or an organization like RIAA? Target has already got their statisticians working on minority report like predictions [slashdot.org]. What if some bureau discovers that some demographic is much more likely to (insert some society destroying activity) and decides to pre-emptively (se